1. Field of the Invention
The present invention relates to processes for a switchable flow-limiting apparatus for limiting the flow of liquids or gases in a patients body, and an apparatus which operates according to the process.
Such apparatuses are used for very varied applications. It is particularly difficult if these apparatuses when in use can no longer be manually adjusted without further action. Particularly for infusion equipment, it is required that the devices furthermore operate absolutely reliably, since a person's life depends on their functional capability. For this reason, the concern in what follows will primarily be with apparatuses which are suitable for use in infusion equipment. However, this is not to preclude the application of the invention to other fields of use.
2. Relevant Prior Art
Infusion systems which are implanted into the body of a patient are already known. They are used for the controlled administration of medicaments. Implantable infusion devices, also termed infusion pumps or medicament pumps, have particular uses in the following aspects of the case: spastic therapy, pain therapy, chemotherapy, and so on. They make possible a direct, continuous administration of medicament (for example, Baclofen or morphine) into the arterial or venous system, and also into the epidural or intraspinal space of the human body. The kind of medicament supply permits such a small dose (0.5-3 ml per 24 hours) that the patient's quality of life is still maintained while the organism is spared side effects which burden it, such as are known in the usual therapies (tablets, drops, injections).
Implantable infusion devices with a fixed, predetermined flow rate have the disadvantage that when the aspects of the case of the patient changes such that a greater or smaller medicament requirement is needed, after implantation of the device, a very expensive pump removal and re-implantation has to be undertaken in order to maintain the patient's quality of life.
Furthermore, it is desired in connection with certain therapies to vary the amount of the medicament which is delivered in a unit of time.
Implantable infusion devices with a battery as an energy source are partially equipped with a controllable flow rate and are electronically controlled. These infusion devices have a normal life, which is limited by the life of the energy supply, of about 36 months in the body of the patient. After that, the removal of the pump is necessary in order to renew the energy source. Thus the duration of functioning of the implant is limited to a relatively short time by the limited life of the energy storage unit (battery or accumulator). These appliances moreover have a very expensive control appliance, which is for the most part considered to be operator-unfriendly, and with which the physician can newly provide the changes and cycles of the flow rate, according to a program.
Legal determinations, for example in Germany, can however forbid a re-implantation; otherwise, a multiple use of the expensive infusion devices would be perfectly possible.
Thus at the present the target group of patients is very limited on cost grounds, and chiefly includes pain therapy in the final stages.
In an advanced version of an infusion device without an electrical energy storage unit, different throttle paths can be combined together (German Laid-Open Patent Application DE-OS 4,123,091), whereby it is possible to set different flow rates. This is achieved by means of a mechanical bistable element, which is set with a key by hand before implantation. The adjustment can also take place after implantation, by a minor operation. The element adjustments then become accessible from outside through a small cut, and the implant itself can remain in the body.
From German Laid-Open Patent Application DE-OS 3,247,232, an infusion system for the supply of medicament is known in which the implanted infusion appliance has a memory device for operating information, able to transmit the stored data to a remote measuring device outside the body of the patient who has an implanted infusion appliance. This remote measuring device and the infusion appliance both have a transmitter and a receiver, so that an instruction for a remotely controlled readiness for operation can be transmitted to the infusion appliance from an instruction transmitting device which is exterior of the body. In the system, various operating data can be interrogated from outside, and the infusion rates can be varied from outside. For this purpose, the infusion appliance has various sensors to monitor the operating data, and a pump which operates in a pulse mode.
From East German Patent DD-PS 293,055, an electromagnetically controlled bistable device is known for implantable infusion pumps which are operated by propellant gas, and which have a bistable device with opposed adjacent operating states. Energy supply here takes place inductively from outside. The bistable device then permits only the two operating states, OFF and ON.
From European Patent EP-PS 0,019,814, a control device for infusion appliances is known, in which control signals are coded in the implanted appliance housing of the infusion appliance.
From European Laid-Open Patent Application EP-OS 0,110,117, there is known an implantable microinfusion pump system, which includes a pump with pulse operation.
From European Patent EP-PS 0,031,850, there is known an implantable, magnetically controlled system for the infusion of pharmaceuticals or medicaments into a living body, with a pressure-actuated apparatus for the delivery of pharmaceuticals, and having a movable bistable element.
From European Patent EP-PS 0,039,124, an implantable infusion appliance which has a flow limiter is known.
From European Patent EP-PS 0,128,703, a micropump for implantation is known, and has an ON/OFF element as a flow controller which is normally closed and which is actuated from an external electromagnet.